Dozens of people have sought emergency medical assistance following reports of a chemical leak in a holiday park swimming pool.
Around 40 people were treated by ambulance crews at the Wild Duck Holiday Park, in Belton, near Great Yarmouth.
Tom Cassidy, spokesman for the park's owners Haven Holidays, said 33 people, including one three-year-old, had been taken to three different hospitals as a "precaution".
He told BBC News: "There was a chemical leak in the swimming pool in the entertainment complex and it was evacuated while police and fire and rescue were on their way.
"The casualties have been described to me as walking wounded.
"Obviously, the park is now in lock down while they try and source the chemical leak."
"It is believed there are around 40 casualties who are being treated by ambulance crews," a Norfolk Constabulary spokesman said.
"The immediate area has been evacuated and a 20m cordon has been put in place around the building, while emergency services deal with the incident."
Police were called to the holiday park along with fire and ambulance crews at 14:35 BST on Sunday (21 June).
News of the medical operation was being shared on Twitter by Nigel Pickover, editor of the Norwich Evening News.
According to a recent update, 29 patients are being treated on site and eight patients have been taken to the James Paget University Hospital in Great Yarmouth.
The Wild Duck Holiday Park is described as a "Norfolk holiday park in a natural woodland setting" on its website.
Its website also states: "Our turquoise pools are a great place to go for a swim...Our indoor pool is heated - great for those rainy days. Take a swim or have a splash at our at our pool party. We even have some paddling areas for toddlers."